Two Lineages of Dengue Virus Type 2, Brazil

rates of nulliparous (empty and unpigmented abdomens) (9) adult midges observed when suction light traps (Onderstepoort Veterinary Institute, Onderstepoort, South Africa) were used on cattle farms during April– May 2007 (4). We identifi ed a breeding site for the primary BTV vector in a cowshed in northern Europe (10). Vectors feed on blood, overwinter inside cowsheds (1), lay eggs, and larvae develop under such conditions. These observations could explain the persistence of BTV from year to year despite fairly harsh winters. Hygienic measures on farms could reduce midge populations and improve effi cacy of vaccination campaigns against BT in Europe. We strongly recommend that such integrated control strategies be evaluated. Removal of residual animal feed and feces on farms and of material from silage structures and sheds, particularly deposits of manure adhering to walls of sheds and used litter, are simple and inexpensive measures that should be implemented. However, their success will depend on active participation by farmers.